Certain conventional air conditioning and refrigeration systems use sealed systems to move heat from one location to another. Certain sealed systems may perform either a refrigeration cycle (e.g., to perform a cooling operation in an appliance such as a refrigerator) or a heat pump cycle (e.g., to heat an indoor room) depending on the appliance and the desired direction of heat transfer. However, the operating principles of both cycles or modes of operation are identical.
Specifically, sealed systems include a plurality of heat exchangers coupled by a fluid conduit charged with refrigerant. A compressor continuously compresses and circulates the refrigerant through the heat exchangers and an expansion device to perform a vapor-compression cycle to facilitate thermal energy transfer. In most sealed systems, an electric motor directly drives the compressor to compress a refrigerant. Notably, the compression process exerts a very uneven load on the motor. For example, during the compression part of the cycle the load torque increases dramatically, and after the high pressure gas is discharged the other half of the cycle has very little load. This variation in load torque causes variation in the rotor speed during the compression cycle, and thus lots of noise and vibration, especially at slow speed, such as during startup.
Accordingly, a sealed system that compensates for variations in load torque resulting from a compression cycle would be desirable. More particularly, a system and method for regulating the speed of the compressor motor to reduce noise, vibration, and excessive wear on sealed system components would be particularly beneficial.